1. Field of the Invention
The present invention relates to a device for retaining a medical instrument in engagement with body tissue and, more particularly, to an improved device for maintaining the desired positional relationship between a trocar tube and body tissue.
2. Background of the Related Art
Devices for holding medical instruments in penetrating relationship with body tissue are known. See, for example, U.S. Pat. No. 2,256,942 which discloses an instrument having a fluted or undulated surface for retaining the device in the walls of the bladder or viscus; U.S. Pat. No. 3,750,667 which discloses a device having a thread which serves to measure the depth of introduction of the device into osseous tissue; and U.S. Pat. No. 4,670,008 which discloses a high flux threaded needle for injecting or removing fluids from the body, the needle having a threaded portion to permit easy insertion of the needle and secure the device in the patient.
Threaded structures have also been applied to larger diameter trocars which are used for introducing viewing and surgical instruments into the body. Such trocars are shown and described in U.S. Pat. Nos. 4,601,710; 4,654,030, and 4,902,280. One commercially available trocar includes a cannula having an integrally molded threaded portion for holding the cannula in the patient's skin. Another device marketed under the trademark SURGIGRIP by U.S. Surgical Corporation, Norwalk, Conn., provides a depth penetration indicator adjustable to a desired position along a cannula and including a threaded portion for holding the cannula in the patient's skin.
Such devices are especially useful in open laparoscopy procedures wherein a surgeon inserts a cannula into an opening in body tissue made with a scalpel. The scalpel-made opening may have a greater tendency to leak gas and/or fluid from around the cannula than does a trocar created opening.